Field of the Invention
The present invention relates to a vehicle body frame structure of a motorcycle.
Description of the Related Art
A vehicle body frame structure of a motorcycle in which a pair of right and left front frames being aluminum die cast or aluminum casting including a head pipe are integrated by bolt coupling and a tank rail being an aluminum extrusion molding is bolt-coupled to the front frame to reduce the weight and cost of the whole frame, is disclosed, for example, in Patent Document 1.
[Patent Document 1] Japanese Laid-open Patent Publication No. 2003-170882
However, in the vehicle body frame structure of a motorcycle disclosed in Patent Document 1, the front frame is in an open cross section structure and thus may fail to ensure strength and stiffness as the vehicle body frame.
Further, the vehicle body frame structure of a motorcycle disclosed in Patent Document 1 is configured such that the tank rail is placed adjacent to a plate-shaped portion of the front frame and bolt-coupled thereto (see FIG. 3 in Patent Document 1), and is thus difficult to increase the joint strength between the front frame and the tank rail.
Further, in the vehicle body frame structure of a motorcycle disclosed in Patent Document 1, it is not considered that the tank rail suspends an engine.